<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="app">
      <div class="box">
        <h3>小黑售货机</h3>
        <button @click="fn(5)">可乐5元</button>
        <button @click="fn(10)">咖啡10元</button>
      </div>
      <p>银行卡余额: {{money}} 元</p>
    </div>

    <script src="/js/vue.js"></script>
    <script>
      const app = new Vue({
        el: "#app",
        data: {
          msg: "nihao ",
          money: 999,
        },
        methods: {
          fn(a) {
            this.money -= a;
          },
        },
      });
    </script>
  </body>
</html>
